The human body has a number of internal body lumens or cavities located within, many of which have an inner lining or layer. These inner linings can be susceptible to disease. In some cases, surgical intervention can be required to remove the inner lining in order to prevent the spread of a disease to otherwise healthy tissue located nearby.
Barrett's Esophagus is a disease wherein the healthy inner mucosal lining (stratified squamous epithelium) of the esophagus is replaced with diseased tissue (abnormal columnar epithelium). Barrett's Esophagus results from chronic exposure of the mucosal lining to irritating gastric secretions. In gastroesophageal reflux disease (GERD) the lower esophageal sphincter fails to close properly and gastric secretions or reflux migrate upwards from the stomach to the lower portions of the esophagus exposing the esophagus to gastric secretions which may cause Barrett's Esophagus. The occasional exposure of the esophagus to gastric secretions is not harmful, but chronic exposure can irritate the mucosal lining and create abnormal mucosal cells. In a certain percentage of the population, the abnormal cells can be a precursor to the development of esophageal cancer. Esophageal cancer is one of the most lethal of all cancers and initial diagnosis is difficult without a visual inspection of the esophagus.
Treatment of GERD ranges from the administration of anti acids in mild cases to surgery such as a Nissen fundoplication. The Nissen fundoplication requires surgical opening of the patient, and the wrapping and suturing of a portion of the stomach around the lower portion of the esophagus to create an esophageal sphincter. Due to age, health, severity of GERD, and other factors, not all patients are candidates for surgery such as the Nissen fundoplication. As a consequence, the medical profession has tended to treat GERD symptoms rather than eradicating the root cause.
When a patient is diagnosed as having Barrett's Esophagus, the traditional treatment has been monitoring of the condition and, as a last resort, surgical removal of the diseased inner mucosal layer. Due to the location of the esophagus within the thoracic cavity and its' close proximity to the lungs, heart and other vascular structures, open surgery is a major undertaking.
Medical experimentation has shown that heating or cooking the inner lining of an organ, body structure, or lumen results in the sloughing off of the heated inner lining and (in many cases) elimination of the disease condition. The mucosal inner lining regrows as healthy tissue if the underlying tissue is not diseased or damaged. There are a variety of methods of heating or cooking the inner lining such as the application of laser light, plasma, resistance heating, the application of warm fluids or warm objects, photodynamic therapy, microwaves, or the application of Radio Frequency (RF) energy to the tissue. An overview of several of these methods of treatment can be found in an article by Richard E. Sampliner entitled "New Treatments for Barrett's Esophagus" which was published in Seminars in Gastrointestinal Disease, Vol 8. No.2 (April), 1997: pp 68-74.
In the above list of possible methods of heating tissue for treatment of Barrett's Esophagus, the application of RF energy has special interest, and in particular, the use of a RF balloon surgical instrument to deliver the energy to a body lumen or cavity. As described in U.S. Pat. No. 2,032,859 by F. C. Wappler, a RF balloon is especially effective for superficial desiccation or heating of tissue, such as the inner layer or lining of a lumen or cavity. The RF balloon described by F. C. Wappler was of monopolar design. Monopolar RF balloon devices use a first pole ground pad placed upon the exterior of the patient and a second (mono)pole balloon electrode placed within the patient and in contact with the diseased tissue. The second pole balloon electrode has an expandable made from a dielectric or non-conducting material, is filled with a conductive fluid, and has an electrode adjacent to the balloon and in contact with the conductive fluid. When applying RF energy to the human body with a bipolar electrosurgical device, it is important to establish firm contact with the tissue to reduce the possibility of burns. The balloon electrode, when inflated within a lumen or cavity within the body, expands outwards to adjust to the irregular contours of the lumen or cavity and firmly contacts the diseased tissue. The use of a non-conducting balloon as the tissue contact surface does not allow the direct coupling of RF energy to the tissue but rather forms a capacitive coupling with the tissue. The capacitive coupling of RF energy results in a gentle heating of the tissue in contact with the balloon electrode.
Whereas the Wappler bipolar RF balloon was indeed a breakthrough, the invention required the insertion of a limp or non-rigid balloon into a body lumen or cavity. Insertion of a non-rigid balloon into a muscular body cavity or lumen was difficult at best. Geddes et al. in U.S. Pat. No. 4,979,948 addressed this issue by describing a monopolar RF Balloon having a rigid elongated member extending longitudinally into the balloon. The elongated member is attached to the proximal base of the balloon and extends freely into the remainder of the balloon. This elongated member provides the necessary rigidity to support the un-inflated balloon during insertion into a body lumen or cavity. Additionally, the second pole electrode of this invention is placed around the elongated member extending within the balloon for contact with the electrolytic or conducting fluid used to expand the balloon.
The Geddes et al. monopolar invention was indeed easier to insert into the patient, but the attachment of the base of the balloon to the elongated member left the proximal end of the balloon free to move relative to the elongated member. When the instrument is placed into a body lumen or cavity and the balloon is inflated, it is possible to bias the distal end of the balloon relative to the distal end of the supporting member. This moves the second pole electrode off center relative to the balloon and may result in uneven heating of the tissue closest to the second pole electrode.
What was needed was an RF balloon instrument that reduces the possibilities of uneven tissue heating or balloon burn through. U.S. Pat. No. 4,7676,258 was issued to Kiyoshi Inokuchi et al. for a flexible monopolar balloon that attaches both proximally and distally to the distal end of a flexible shaft of the instrument. Whereas the Inokuchi et al. monopolar balloon utilized proximal and distal attachment of the balloon to the flexible shaft of the instrument, the monopolar design required the use of a second electrode that is placed on the outer circumference of the patient and the use of a constant flow of cooling fluid. An elongated resilient flexible electrode member (made from conductive material) that extends into an electrosurgical balloon is described in the F. C. Wappler U.S. Pat. No. 2,043,083.
All RF balloon inventions described above are monopolar and require the use of a return pole electrode or pad placed in contact with the exterior of the patient. U.S. Pat. No. 5,578,008 was issued to Shinji Hara for a bipolar balloon catheter wherein both the proximal and the distal end of the RF balloon is attached to the catheter (rigid support member) and has both (bipolar) electrodes located within the balloon. The bipolar RF balloon is fixed relative to both the catheter and reduces the possibilities of uneven heating described above. The bipolar electrode design heats the cooling liquid within the balloon and the heated liquid heats the tissue in contact with the balloon.
It is frequently difficult for a surgeon to access a surgical site, particularly when the goal is to access the surgical site without cutting or opening the patient. Atraumatic access is typically achieved by admitting the surgical instrument into the patient through a natural body orifice, and manipulating or maneuvering the surgical instrument to the desired location. Since the human body rarely has linear passageways or structures, access to a surgical site can require the surgical instrument to bend or flex. As the surgeon is manipulating the surgical instrument around comers to attain access to the surgical site, care must be taken to avoid traumatic tissue damage caused by the instrument. Thus, it would be advantageous to design an RF balloon end effector with a means to help guide the end effector around comers and, more particularly, to guide the end effector around corners when navigating a torturous lumen or passage. A U.S. Pat. No. 5,558,672 by Edwards et al. teaches a porous monopolar RF balloon that has viewing optics that extend from the distal end of the balloon.
It would further be advantageous to provide the surgeon with a RF balloon electrosurgical instrument that can fit down the operating channel of an endoscope enabling the surgeon to visually place the balloon electrode at the surgical site. Shinji Hara in U.S. Pat. No. 5,578,008 and Jackson et al. in U.S. Pat. No. 4,676,258 describe the use of pulses or bursts to deliver energy from the electrosurgical generator to the balloon electrode. What is not disclosed in these inventions is the delivery of pulsed or burst RF electrical energy in a preset pattern to produce specific tissue effects.